Pitfalls of the phase-shift method for determining adsorption isotherms

Pitfalls of the phase-shift method for determining adsorption isotherms in the case of two-step Faradaic reactions involving adsorption at transition metals (alloys)/aqueous solution interfaces are discussed following the recent publication of the paper [J.Y. Chun, J.H. Chun, Electrochem. Commun. 11 (2009) 744]. It is shown how the pitfalls of the method are generated by improper analysis of impedance data resulting in at least disputable values characterizing adsorption isotherms (equilibrium constant, K  , standard free energy, ΔGθ0, and interaction parameter between adsorbed species, g).